Stratifying risk outcomes among adult COVID-19 inpatients with high flow oxygen: The R4 score

G. M. Aguirre-García, D. Ramonfaur, G. Torre-Amione, M. T. Ramírez-Elizondo, R. Lara-Medrano, J. F. Moreno-Hoyos, E. S. Velázquez-Ávila, C. A. Diaz-Garza, V. M. Sanchez-Nava, F. Castilleja-Leal, G. M. Rhoades, M. F. Martínez-Reséndez

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Background: High flow oxygen therapy (HFO) is a widely used intervention for pulmonary complications. Amid the coronavirus infectious disease 2019 (COVID-19) pandemic, HFO became a popular alternative to conventional oxygen supplementation therapies. Risk stratification tools have been repurposed –and new ones developed– to estimate outcome risks among COVID-19 patients. This study aims to provide a simple risk stratification system to predict invasive mechanical ventilation (IMV) or death among COVID-19 inpatients on HFO. Methods: Among 529 adult inpatients with COVID-19 pneumonia, we selected unadjusted clinical risk factors for developing the composite endpoint of IMV or death. The risk for the primary outcome by each category was estimated using a Cox proportional hazards model. Bootstrapping was used to validate the results. Results: Age above 62, eGFR under 60 ml/min, room air SpO2 ≤89 % upon admission, history of hypertension, history of diabetes, and any comorbidity (cancer, cardiovascular disease, COPD/ asthma, hypothyroidism, or autoimmune disease) were considered for the score. Each of the six criteria scored 1 point. The score was further simplified into 4 categories: 1) 0 criteria, 2) 1 criterion, 3) 2-3 criteria, and 4) ≥4 criteria. Taking the first category as the reference, risk estimates for the primary endpoint were HR; 2.94 [1.67 – 5.26], 4.08 [2.63 – 7.05], and 6.63 [3.74 – 11.77], respectively. In ROC analysis, the AUC for the model was 0.72. Conclusions: Our score uses simple criteria to estimate the risk for IMV or death among COVID-19 inpatients with HFO. Higher category reflects consistent increases in risk for the endpoint.

Original languageEnglish (US)
Pages (from-to)200-206
Number of pages7
Issue number3
StatePublished - May 1 2023


  • Coronavirus
  • Oxygen inhalation therapy
  • Respiratory distress syndrome
  • Risk
  • Inpatients
  • SARS-CoV-2
  • COVID-19/epidemiology
  • Humans
  • Adult
  • Oxygen/therapeutic use
  • Communicable Diseases

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine


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